ARM: entry: Block IRQs in early IRQ context
When dabt, pabt or und exceptions occur on ARM, ordinary
interrupts (IRQs) can still happen. This isn't nice for the
kernels context tracker, which expect (when using generic
entry at least) that any nested IRQs happens
between irqentry_enter() and irqentry_exit(), else it
thinks something is fishy.
This change blocks interrupts in the pabt, dabt, und and
abt exception paths (all of them really) by unconditionally
setting PSR_I_BIT in the early exception handler, until
after context has been established with irqentry_enter()
and before it is exited with irqentry_exit(). Inside the
context-tracked exception handler we enable IRQs again,
and once we leave it we disable them while exiting the
exception.
The local_irq_disable() in bad_mode() can be dropped
since we are now disabling IRQs in the early assembly
exception handler for all exceptions.
This seems like not perfect: it seems an interrupt
could still occur right before CPSR is set, or right after
the userspace registers are restored in ret_from_exception.
I would like to know if there is some
way to set up these exceptions to inherently block IRQs
when handled, until we explicitly allow them between
irqentry_enter() and irqentry_exit() or if this is simply
the best we can do on ARM for these exceptions to make the
context tracker happy.
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
3 files changed
